EP0047406B1

EP0047406B1 - A method of forming a lead styphnate compound plus barium nitrate in situ, for use in a priming mix

Info

Publication number: EP0047406B1
Application number: EP81106388A
Authority: EP
Inventors: Venkataramaraj Subbaraj Urs
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1980-08-29
Filing date: 1981-08-17
Publication date: 1985-08-14
Also published as: EP0047406A3; ZA814518B; CA1152748A; US4336084A; ATE14870T1; IL63472A; JPS5777090A; EP0047406A2; AU541230B2; DE3171810D1; NZ197544A; AU7277181A

Abstract

An improved method for producing known primer constituents lead styphnate and barium nitrate, in situ, plus water. The process is carried out by reacting effective amounts of trinitroresorcinol (TNR), with barium hydroxide, or barium carbonate, and lead nitrate in water.

Description

This invention relates to a method of forming a lead styphnate compound and barium nitrate, in situ, for use in a priming mix. More specifically, the method of this invention involves the reaction of trinitroresorcinol, with barium hydroxide compounds and lead nitrate, to produce the lead styphnate and barium nitrate, plus an additional amount of water.
Typical percussion primer mixtures for use in shot shell, rim fire and center fire ammunition contain effective amounts of lead styphnate which is a primary high explosive, sensitizers such as tetracene, boosters such as pentaerythritol tetranitrate (PETN), oxygen-donating compounds such as barium nitrate or lead nitrate, and fuels such as aluminum powder, antimony sulfide, and calcium silicide. These ingredients are blended together in water for safety purposes, and are wet primed into a shot shell or center-fire primer cup or a rim fire case rim. The primed charges are then dried and thus made ready for use. In the case of rim fire primers, a frictionator such as ground glass may be added to the mixture.
The primary high explosive, lead styphnate, which is used in the above-noted primer manufacturing process, is generally prepared in 15,876 to 31,751 kg batches, and smaller portions of the bulk supply of the lead styphnate are transferred to the mixing and blending device with the other constituents to produce the primer mix. Since lead styphnate is a highly percussion sensitive material, particularly when dry, the handling and storing of large bulk quantities of 15,876 to 31,751 kg of this material requires substantial safety precautions.
The bulk supply of lead styphnate is typically produced by reacting trinitroresorcinol with an excess of sodium hydroxide or magnesium oxide and acetic acid to form sodium or magnesium styphnate: The sodium or magnesium styphnate solution is then heated to about 60°C and a large excess of aqueous solution of lead nitrate is added to produce a lead styphnate precipitate. The lead styphnate is then filtered out of the solution and washed free of soluble salts. The filtrate, which contains excess lead nitrate and the sodium or magnesium salts, as well as the wash waters, are then disposed of as waste materials. It will be apparent from the above, that the separate preparation of lead styphnate is undesirable since it takes time, utilizes expensive reagents, produces a waste material containing many of the process reagents, and can create an environmental pollution problem concerning disposal of the waste materials. In addition to the above-noted process for producing lead styphnate, a number of other processes for the production of lead styphnate are reviewed and discussed in U.S. Patent No. 3,983,149, to Joseph F. Kenney granted September 28, 1976.
The foregoing clearly points out the disadvantages of wastefulness of both time and materials, the additional expense, the safety problems, and the potential pollution problems which are all attendant to the prior art processes for producing lead styphnate for use in priming compositions.
The above-noted U.S. Patent No. 3,983,149 to Kenney, as previously observed, presents an extensive review of the prior art processes for forming lead styphnate, and their attendant disadvantages. This patent then offers as a solution to the prior art problems, a method of producing lead styphnate in situ in a Hobart mixer, which is the device commonly used in the trade in blending the priming composition constituents prior to the actual placement of the priming charges in the primer cups or cartridge case rims. The Kenney process involves the reaction of styphnic acid (trinitroresorcinol) with a lead compound, such as lead oxide, lead hydroxide, basic lead carbonate, or lead carbonate, the reaction taking place in water and resulting in the in situ formation of lead styphnate plus water, and, in some instances with certain reagents, carbon dioxide is also formed. After the lead styphnate has been formed, the remaining primer constituents are added to the Hobart mixer and blended to form the priming mix. It should be noted that some of the priming constituents, such as gum arabic, tetracene, blue dye, and some fuels such as calcium silicide can be incorporated with the styphnic acid before the lead compound is added, since these compounds will not enter into the ensuing reaction. On the other hand, it should also be noted that the oxygen donor, such as lead nitrate or barium nitrate should definitely not be added until after the lead styphnate has been formed. The Kenney method also requires that pure styphnic acid be used in the reaction, since the use of commercial styphnic acid results in an excessively sticky mixture which clings to the charging equipment and prematurely hardens so that the mixture cannot be stored overnight.
Another method described in British Patent Specification No. 2015494 A is based on the concept of the respective parent specification 37013/76, according to which a primary explosive is to be formed in a preformed body of another explosive. On page 1, lines 65 to 72, there is explained in detail the meaning of the expression "production in situ" as used in that specification. This meaning is corroborated by figs. 1 to 5 from which it can be seen that the primary explosive, specifically lead azide, is formed in a detonator case which comprises already a charge of secondary explosive.
The disclosure on page 34to 89 of this prepubli- cation refers to a "premix" technique according to which staphnic acid powder is first mixed with a basic lead compound in powder form, this mixture being allowed to react by adding a suitable reaction medium.
As basic lead compound there are mentioned lead oxide, lead hydroxide and lead carbonate. In this system the basic lead compound is reacting directly with the styphnic acid and therefore the afore-mentioned disadvantages cannot be avoided.
Another publication (British Patent Specification 1569874) is concerned with the production of a primary explosive within an explosive device like the one mentioned in subclaim 26.
This prior art comprises examples only for preparing lead styphnate by reaction of sodium styphnate with lead nitrate whereby a sodium nitrate is formed as by-product (see example 1a) or by reacting staphnic acid with lead carbonate or lead oxide in the presence of barium nitrate (see example 1b), in this reaction no by-product being formed but C0₂. Again, the known difficulties in preparing lead styphnate and handling and storing large bulk quantities of it cannot be overcome by this prior art.
According to "Analytical Chemistry", 27 (1955), pp. 2014 and 2015, lead styphnate is produced in a very pure form by adding dropwise a dilute solution of sodium hydroxide to a mixed solution of styphnic acid and lead nitrate in 50% aqueous ethyl alcohol.
From this teaching nothing can be learned as regards the technical problem to be solved underlying the present invention.
Furthermore it has to be taken into consideration that the oxidizing compounds known from the prior art, i.e. sodium nitrate and lead nitrate, are both hygroscopic, whereas the barium nitrate formed in situ according to the invention is non- hygroscopic. Compounds like sodium nitrate and lead nitrate tend to pick up water when stored for prolonged periods and hence becomes inactive. In contrast, the intimate mixtures of lead styphnate and barium nitrate prepared according to the invention have an extremely long shelf life because they do not tend to become inactive due to water absorption.
The method according to the invention is characterized in that trinitroresorcinol is reacted with an oxygen-bearing compound selected from the group consisting of barium hydroxide compounds in the presence of lead nitrate.
This in situ reaction can be carried out in a Hobart mixer.
The remaining priming constituents are then added to the formed intimate mixture of lead styphnate and barium nitrate and the primer mix is blended and ready to use in priming cartridges. In the method of this invention there are no waste products, no need to make larger than necessary amounts of lead styphnate than needed to complete a priming run, whereby considerable cost savings are realized along with reduced safety hazards. The method of this invention permits the use of conventional commercial grade trinitr.o-resorcinol, although it also can be performed with the purified TNR, which is an absolute requirement in the Kenney process referred to above. By forming both the lead styphnate and the barium nitrate in situ in a single reaction, there is achieved an intimate admixture of these two ingredients which is not likely to be achieved by physically blending these two constituents. In the method of this invention, the lead styphnate and barium nitrate are formed in situ by reacting TNR with barium oxide, barium hydroxide or barium carbonate and lead nitrate in the presence of water. The end products of this reaction are lead styphnate, barium nitrate and water. When the reactants are combined in water, an exothermic reaction immediately ensues with the temperature in the mixture reaching between 54,4 to 87,8°C in 60 to 100 seconds, the actual temperature reached being dependent upon the ambient temperature. The exothermic condition causes the reaction to go to completion in the very short time span of one to two minutes. After reaching the temperature peak, the mix temperature is observed to drop to as low as 37,8°C within the next two to three minutes. Breaking down the reaction stepwise, the TNR exothermically reacts with the barium hydroxide to form barium styphnate, which immediately then reacts with the lead nitrate to form lead styphnate, and barium nitrate. Two molecules of water are formed for each molecule of lead styphnate and barium nitrate, one molecule of water being free and the other being loosely bonded to the lead styphnate, thus forming lead styphnate monohydrate.
The diagramed reaction is as follows:
The reaction is, in general terms, carried out in the Hobart mixer as follows. Weighed amounts of TNR, barium hydroxide, and lead nitrate are put into the Hobart mixer in relatively dry form and a small amount of water, preferably five to ten percent by weight of the dry solids, is added to the mixer. The mixer is activated to stir the mixture during the reaction. After five minutes the mixer is stopped and the mixing paddle is cleaned to return mix adhering thereto to the remaining mixture. The mixing is then resumed for another ten minutes to assure completeness of the chemical reactions. After the subsequent mixing period often minutes, the adhering mix is knocked down into the mixer, the mix by this time being at ambient temperature, and weighed quantities of remaining priming constituents, such as tetracene, PETN, antimony sulfide, aluminum, and a small amount of barium nitrate are added to the mix. A five percent solution of polyvinyl alcohol is added to the mixer to bring the moisture content of the mix suitable for working into primer cups. The entire mix is then blended for ten minutes to achieve admixture of all of the constituents, after which the priming mixture may be worked into primer cups in a conventional manner. The primer cups are foiled and dried, whereafter they are ready to be inserted into cartridges.
Specific examples of methods of forming priming mixes in accordance with this invention are as follows.

Example 1

A three litre Hobart mixer was charged with 441 grams of lead nitrate, 252 grams of barium hydroxide monohydrate, 225 grams of antimony sulfide, and 102 grams of barium nitrate. These ingredients all were charged in a dry state and had been screened through a 30 mesh sieve. These ingredients were then mixed for five minutes in the Hobart mixer. The equivalent of 327 grams dry weight of wet TNR (making allowance for the moisture content) was added to the ingredients in the Hobart mixer along with 20 grams of water. Blending was then commenced and the exothermic reaction temperature rise was immediately apparent. Blending in the mixer was continued for five minutes after which the blending was stopped and the adherant mix was cleaned off of the mixing blade. Blending was then resumed and continued for ten minutes. The resultant mix was then analysed and showed to contain lead styphnate, barium nitrate, antimony sulfide, and water. The pH of the mix was between 2 and 5, the acidity thereof demonstrating complete reaction of the barium hydroxide. Twenty five milliliters of five percent polyvinyl alcohol solution in water was then added to the mix, followed by 60 grams (dry weight) of te_tra- cene (using wet material, but making allowance for the water content), 75 grams of PETN and 90 grams of aluminum powder. Mixing was then continued for ten minutes to obtain a uniformly blended mix. The moisture content of the final mix was about fifteen percent. Chemical analysis of the mix showed the following percentages of the various components on a dry basis:
Shot shell primer cups were primed with the primer mix in the conventional wet priming procedure. The assembled primers exhibited good sensitivity, with three hundred of a total of three hundred all firing when a 56,698 g steel ball was dropped from a height of 172,64 mm on each primer mounted in a steel die. Five hundred of these primers were then assembled in 0,304 mm, 69,85 mm plastic shotshell tubes, using WC 490 Winchester nitrocellulose smokeless powder, 2,022 g by weight, a cup and molded fiber wad, a low density polyethylene liner, 35,436 g lead shot, #4 chilled, with a six segment pie crimp closure. These five hundred shotshells were fired in five different shotguns at temperatures of 51,7; 76,7; -17,8 and -40°C. No misfires, hangfires or squibs were experienced in this test, and all of the rounds fired satisfactorily.

Example 2

A three litre Hobart mixer was charged with 441 grams of lead nitrate, 252 grams of barium hydroxide monohydrate, 147 grams of barium nitrate, and 240 grams of antimony sulfide, these ingredients having been charged in the dry state after having been screened through a 30 mesh sieve. To the above mixture was added 327 grams dry weight of TNR, using wet TNR but making allowance for its water content, and 20 grams of water. The mixture was then blended in the Hobart mixer for five minutes, after which the mixer blade was cleaned, and blending then continued for an additional ten minutes. Then 25 millilitres of a 5 percent polyvinyl alcohol solution was added, along with 75 grams, dry weight, of tetracene, using wet material but making allowance for its water content, and 90 grams of PETN. Mixing then continued for an additional ten minutes. The mix was then examined for gritti- ness and uniformity. If the mix is found to be gritty and non-uniform, mixing can continue for an additional five to ten minutes. The moisture content of the blended mix was about fifteen percent. This mix was then charged into center fire pistol primer cups by the conventional wet priming process, foiled, fitted with anvils, and dried. Sensitivity tests performed on these assembled primer cups when assembled in caliber, 38 Special cartridge cases demonstrated satisfactory sensitivity characteristics.

Example 3

A rim fire priming mix was formed by charging a Hobart mixer with 509.2 grams of lead nitrate, 293.7 grams of barium hydroxide monohydrate, these ingredients having been pre-screened as outlined in the previous examples. To these ingredients there was added 376.9 grams of TNR, dry weight using wet TNR but making allowance for its water content, and 20 grams of water. These ingredients were blended in the Hobart mixer for a total of 15 minutes using the two step blending procedure described in the previous examples, and then 25 millilitres of a 5% polyvinyl alcohol solution, 105 grams of lead peroxide, and 330 grams of glass powder were added to the Hobart mixer. The contents of the Hobart mixer were then blended until a uniform texture mix was achieved.
Using a perforated metal charge leaf, 0.0162 to 0.0207 g (.25 to .32 grain) pellets of the priming mix were dropped into .22 caliber rim fire cartridge cases and the primer pellets were spun into the rims of the cases. The in-place primers were then dried and tested by the drop ball sensitivity procedure. The sensitivity was found to be uniformly acceptable indicating that the primed cases were suitable for loading into .22 caliber rim fire ammunition.
The above-outlined examples indicate the operability of primer compositions and the lead styphnate and barium nitrate constituents thereof formed in accordance with this invention for priming shotshell, center fire, and rim fire ammunition.
It should be noted that in the chemical reactions performed in the examples outlined above, for every molecule of lead styphnate formed, one molecule of barium nitrate and two molecules of water are also formed. Examination of the lead styphnate crystals formed in the reaction shows them to be hexagonal, and apparently lead styphnate monohydrate molecules. Therefore, each time a lead styphnate monohydrate molecule is formed, there is a free molecule of water also formed. This results in a free moisture content of 3.8% and a total water content of 8% when dry initial reactants are used. Thus, the reaction forms water, which in turn, contributes to desensitiza- tion of the lead styphnate formed, during the preparation of the priming mix.
It will be readily appreciated that this invention results in the formation of lead styphnate and barium nitrate, in situ, in an intimate admixture, with lower costs, no waste by-products, and therefore, no pollution problems relating to disposal of waste by-products. This invention also provides for increased safety and reduced hazard since the primary explosive need not be produced, stored or handled in large bulk amounts, and need only be produced in batch amounts which will be utilized in a subsequent priming operation.
It should be noted that electrically fired primer mixes may also be formed using the process of this invention simply by adding to the priming mix a conductor, such as carbon.

Claims

1. A method of forming a lead styphnate compound plus barium nitrate in situ, for use in a priming mix, said method being characterized in that trinitroresorcinol is reacted with an oxygen-bearing compound selected from the group consisting of barium hydroxide compounds in the presence of lead nitrate.

2. A method according to claim 1, characterized in that water is present in the reaction mixture.

3. A method according to claims 1 and 2, wherein said barium hydroxide compound is barium hydroxide monohydrate.

4. The mixture of lead styphnate compound and oxygen-donating compound produced by the method of claims 1 to 3.